Organic light emitting display device and driving method thereof

ABSTRACT

An organic light emitting display device, can include a panel, a driving unit driving the panel, a timing controller controlling the driving unit, a power supply supplying power to the panel, a current detection unit detecting a current flowing through power line wiring of the panel and outputting the detected currents, and a power controller comparing the detected current with a current value configured internally and outputting a shutdown signal which turns off the power supply if the detected current exceeds the predetermined current value.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of co-pending U.S. patent applicationSer. No. 13/718,739 filed Dec. 18, 2012, which claims priority to KoreanPatent Application Nos. 10-2012-0106563 filed Sep. 25, 2012 and10-2012-0106565 filed Sep. 25, 2012, all of which are herebyincorporated by reference, as if they are fully set forth herein.

BACKGROUND OF THE INVENTION

1. Technical Field

This document relates to an organic light emitting display device and adriving method of the device.

2. Background Art

An organic light emitting element used for an organic light emittingdisplay device refers to a self-light emitting element in which a lightemitting layer is formed between two electrodes on the substrate of thedevice. Organic light emitting display devices are classified intotop-emission type, bottom-emission type, dual-emission type, and so onaccording to a direction along which light is emitted. Alternatively,organic light emitting devices can be divided into passive matrix typeand active matrix type according to a driving method employed.

A sub-pixel disposed in an organic light emitting display panelcomprises a transistor unit including a switching transistor, a drivingtransistor, and a capacitor; and an organic light emitting diodeincluding a lower electrode connected to the driving transistor includedin the transistor unit, an organic light emitting layer; and an organiclight emitting diode including a upper electrode.

An organic light emitting display panel exhibits light intensity varyingin proportion to the amounts of a current flowing through the organiclight emitting diode. Since organic light emitting display panelsrequire a large amount of current compared with liquid crystal displaypanels, in the event of short circuit at power terminals, an excessiveamount of current flows into the elements of the respective sub-pixels.Various factors cause short circuit at power terminals, which includenot only internal, structural factors such as particles introduced intothe organic light emitting display panel during a manufacturing process(or a module process), cracks, misalignment of pad units, and narrowwiring layout but also external factors such as static electricity.

If an excessive current flows into a sub-pixel due to short circuit atpower terminals, elements of the corresponding sub-pixel are burnt out.Burning out in a small region may not be perceived at its early stagebut neighboring sub-pixels are gradually burnt out as the organic lightemitting display panel continues to operate.

In this respect, there are high chances short circuit at power terminalsburns out sub-pixels of an organic light emitting display panel andsubsequently leads to a fire; therefore, a means for preventing shortcircuit has to be provided.

SUMMARY OF THE INVENTION

The present invention has been made in an effort to provide an organiclight emitting display device comprising a panel; a driving unit drivingthe panel; a timing controller controlling the driving unit; a powersupply supplying power to the panel; a current detection unit detectinga current flowing through power line wiring of the panel and outputtingthe detected current; and a power controller comparing the detectedcurrent with a current value configured internally and outputting ashutdown signal which turns off the power supply if the detected currentexceeds the predetermined current value.

Another aspect of the present invention provides an organic lightemitting display device comprising a panel including power line wiringwired up for individual blocks; a driving unit driving the panel; atiming controller controlling the driving unit; a power supply supplyingpower to the panel; a current detection unit detecting a current flowingthrough the power line wiring of each block and outputting the detectedcurrent of the block; and a power controller comparing detected currentsof the individual blocks with each other and outputting a shutdownsignal which turns off the power supply if a current higher or lowerthan the currents of the other blocks is detected.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompany drawings, which are included to provide a furtherunderstanding of the invention and are incorporated on and constitute apart of this specification illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a block diagram of an organic light emitting display deviceaccording to the present invention;

FIG. 2 is a circuit diagram of a sub-pixel;

FIG. 3 is a block diagram of a power supply controller according to afirst embodiment of the present invention;

FIG. 4 is a first circuit diagram illustrating a power controller;

FIG. 5 is a second circuit diagram illustrating a power controller;

FIG. 6 is a waveform diagram illustrating operation of a powercontroller and a power supply in response to a blank interval;

FIG. 7 is a waveform diagram illustrating operation of a powercontroller and a power supply in response to an interval for whichsensing data are provided;

FIG. 8 illustrates output states of a power supply according to acomparison result between a detected current value and a configuredcurrent value;

FIG. 9 is a block diagram of a power supply controller according to amodified example of a first embodiment;

FIG. 10 illustrates an organic light emitting display device implementedaccording to a first embodiment of the present invention;

FIG. 11 is a flow diagram illustrating a method for operating an organiclight emitting display device according to a first embodiment of thepresent invention;

FIG. 12 is a block diagram of a power supply controller according to asecond embodiment;

FIG. 13 illustrates output states of a power supply according to acomparison result between detected currents of individual blocks;

FIG. 14 illustrates an organic light emitting display device implementedaccording to a second embodiment of the present invention;

FIG. 15 is a flow diagram illustrating a method for operating an organiclight emitting display device according to a second embodiment of thepresent invention;

FIG. 16 is a block diagram of an organic light emitting display deviceaccording to a third embodiment of the present invention;

FIG. 17 is a first example of a compensation voltage supply;

FIG. 18 is a second example of a compensation voltage supply;

FIG. 19 is a circuit diagram of a sub-pixel;

FIG. 20 is an example of a compensation circuit of FIG. 19;

FIG. 21 is a driving waveform diagram of a sub-pixel of FIG. 20;

FIG. 22 is a block diagram implementing a circuit according to a thirdembodiment of the present invention;

FIG. 23 is a circuit diagram of a compensation voltage supply and avoltage sensing unit of FIG. 22;

FIG. 24 illustrates an organic light emitting display device implementedby using constituting elements according to a third embodiment of thepresent invention;

FIG. 25 illustrates a maximum and a minimum level of a referencevoltage;

FIG. 26 illustrates an allowable range of a reference voltage;

FIG. 27 illustrates output states of a power supply according to ashutdown signal;

FIG. 28 is a flow diagram illustrating a method for operating an organiclight emitting display device according to a third embodiment of thepresent invention;

FIG. 29 is a block diagram of an organic light emitting display deviceaccording to a fourth embodiment of the present invention;

FIG. 30 illustrates a current sensing unit and an analog-to-digitalconverter of FIG. 29;

FIG. 31 is a circuit diagram of a current sensing unit of a first blockof FIG. 30;

FIG. 32 is a block diagram of an analog-to-digital converter, a timingcontroller, and a power supply;

FIG. 33 is a waveform diagram illustrating operation of ananalog-to-digital converter in response to a blank interval;

FIGS. 34 and 35 illustrate output states of a power supply according toa decision of a timing controller; and

FIG. 36 is a flow diagram illustrating a method for operating an organiclight emitting display device according to a fourth embodiment of thepresent invention.

DETAIL DESCRIPTION OF THE INVENTION

Reference will now be made in detail embodiments of the inventionexamples of which are illustrated in the accompanying drawings.

In what follows, preferred embodiments of the present invention will bedescribed in detail with reference to appended drawings.

<First embodiment>

As shown in FIGS. 1 and 2, an organic light emitting display devicecomprises an image processing unit 120, a power supply 125, a timingcontroller 130, a data driving unit 150, a scan driving unit 140, apanel 160, a current detection unit 170, and a power controller 180.

An image processing unit 120 provides a timing controller 130 with avertical synchronization signal (Vsync), a horizontal synchronizationsignal (Hsync), a data enable signal (DE), a clock signal (CLK), and adata signal (DATA). The image processing unit 120 is formed in a systemboard 110.

The timing controller 130 controls an operation timing of the datadriving unit 150 and the scan driving unit 140 by using timing signalssuch as the vertical synchronization signal (Vsync), the horizontalsynchronization signal (Hsync), the data enable signal (DE), and theclock signal (CLK). Since the timing controller 130 is capable ofdetermining a frame interval by counting the data enable signal (DE)during one horizontal interval, the vertical synchronization signal(Vsync) and the horizontal synchronization signal (Hsync) provided fromthe outside can be omitted. Control signals generated at the timingcontroller 130 include a gate timing control signal (GDC) forcontrolling the operational timing of the scan driving unit 140 and adata timing control signal (DDC) for controlling the operational timingof the data driving unit 150. The gate timing control signal (GDC)includes a gate start pulse, a gate shift clock, and a gate outputenable signal. The data timing control signal (DDC) includes a sourcestart pulse, a source sampling clock, and a source output enable signal.

The scan driving unit 140 shifts the level of a gate driving voltage inresponse to the gate timing control signal (GDC) provided from thetiming controller 130 and generates a scan signal in a sequentialmanner. The scan driving unit 140 provides a scan signal through scanlines (SL) connected to sub-pixels (SPs) included in the panel 160.

The data driving unit 150 performs sampling of the data signal (DATA)provided from the timing controller 130 in response to the data timingcontrol signal (DDC) provided from the timing controller 130 and latcheson the sampled data signal and transforms the latched, sampled datasignal into the data of a parallel data system. The data driving unit150 transforms the data signal (DATA) into a gamma reference voltage.The data driving unit 150 provides the data signal (DATA) through thedata lines (DLs) connected to sub-pixels (SPs) included in the panel160.

The panel 160 comprises sub-pixels disposed in the form of a matrix.Sub-pixels consist of red, green, and blue sub-pixels; in some cases,white sub-pixels are included. A panel 160 incorporating whitesub-pixels can emit white light even if light emitting layers ofindividual sub-pixels do not emit red, green, and blue light. In thiscase, the white light is converted into red, green, and blue light by anRGB color filter.

Meanwhile, sub-pixels included in the panel 160 may be comprised asshown in FIG. 2. One sub-pixel comprises a switching transistor SW, adriving transistor DR, a capacitor Cst, a compensation circuit CC, andan organic light emitting diode D. The switching transistor (SW)performs a switching operation in such a way that a data signal providedthrough a first data line DL1 in response to a scan signal providedthrough a first scan line SL1 is stored in the capacitor as a datavoltage. The driving transistor DR operates to have a driving currentflow between a first power line wiring VDD and the ground GND. Thecompensation circuit CC compensates for a threshold voltage of thedriving transistor DR. The compensation circuit CC comprises one or moretransistor and capacitor. The compensation circuit CC can be implementedin various ways; specific descriptions and examples of the compensationcircuit are not provided furthermore. The organic light emitting diode Doperates to emit light according to a driving current developed by thedriving transistor DR.

One sub-pixel is formed to have a 2T (Transistor) 1C (Capacitor)structure comprising a switching transistor SW, a driving transistor DR,a capacitor Cst, and an organic light emitting diode D. In case acompensation circuit CC is further incorporated, the sub-pixel may forma 3T1C, 4T2C, or 5T2C structure. A sub-pixel having the structure abovecan form a top-emission type, bottom-emission type, or dual-emissiontype depending on a structure employed.

The power supply 125 converts an external voltage supplied from theoutside into a first voltage (for example, 20 V level), a second voltage(for example, 3.3V level), and a low voltage (for example, 0 V level),and so on. The first voltage, being supplied to a first power linewiring VDD, is a drain level voltage; the second voltage, being suppliedto a second power line wiring VCC, is a collector level voltage; and thelow level voltage is supplied to the ground GND and is a base levelvoltage. The power supply 125 is formed in the system board 110 togetherwith the image processing unit 120. The output voltage of the powersupply 125 is used for the image processing unit 120, the timingcontroller 130, the data driving unit 150, the scan driving unit 140,and the panel 160.

The current detection unit 170 detects a current flowing into the panel160 through the first power line wiring VDD and outputs the detectedcurrent. The current detection unit 170 detects a current flowing intothe panel 160 through the first power line wiring VDD and provides thedetected current to the power controller 180. The current detection unit170 can be realized with conventional OP amps and the detected currentmay be an analog value but the present invention is not limited to theabove.

The power controller 180 generates a shutdown signal SDS according to acurrent detected by the current detection unit 170. The power controller180 outputs the shutdown signal SDS when the detected current reaches anovercurrent, thereby turning off the power supply 125. In other words,the whole output of the power supply 125 is shut down.

The current detection unit 170 and the power controller 180 describedearlier comprise a short detection circuit which detects occurrence ofshort circuit at the power supply and in the event of short circuit,turns off the power supply 125. Various factors cause short circuit atpower terminals, which include not only internal, structural factorssuch as particles introduced into the panel 160 during manufacturingprocess (or module process), cracks, misalignment of pad units, andnarrow wiring layout; but also external factors such as staticelectricity.

If an excessive current flows into a sub-pixel due to short circuit atpower terminals, elements of the corresponding sub-pixel are burnt out.Burning out in a small region may not be perceived at its early stagebut neighboring sub-pixels are gradually burnt out as the panel 160continues to operate. To prevent the above problem, the short detectioncircuit controls the power supply 125 in such a way to remove thepossibility of generating a fire at the panel 160, where specificdescriptions thereof are given below.

In this respect, there are high chances short circuit at power terminalsburns out sub-pixels of an organic light emitting display panel andsubsequently leads to a fire; therefore, a means for preventing theshort circuit has to be provided.

In what follows, an organic light emitting display device according tothe present invention will be described in more detail.

<First embodiment>

As shown in FIG. 3, the circuit for controlling the power supply 125comprises a timing controller 130, a current detection unit 170, and apower controller 180.

The current detection unit 170 detects a current flowing through a firstpower line wiring VDD and supplies the detected current to the powercontroller 180. The current detection unit 170 detects a current flowingthrough the first power line wiring VDD periodically or aperiodically.If the current detection unit 170 detects a current flowing through thefirst power line wiring VDD regularly and it is not controlled by aparticular device, it can be implemented by using OP amps. On the otherhand, if the current detection unit 170 detects a current flowingaperiodically through the first power line wiring VDD and it iscontrolled by a particular device, it can be implemented by using OPamps and switches. In this case, a switch detects a current inaccordance with a control signal. Meanwhile, the current detection unit170 may further comprise an analog-to-digital converter according to thestructure of the power controller. At this time, the analog-to-digitalconverter converts an analog current value to a digital current valueand displays the converted current.

The timing controller 130 provides a sensing signal SS to the powercontroller 180. The timing controller 130 can not only provide a panelwith sensing data through a data driving unit periodically but alsoprovide the power controller 180 with the sensing signal SS in order forthe power controller 180 to operate in synchronization with a timing atwhich the sensing data is displayed. On the other hand, the timingcontroller 130 can provide the sensing signal SS to the power controller180 in order for the power controller 180 to operate for blank intervalsexcluding an image display interval of the panel.

The power controller 180 receives a detected current from the currentdetection unit 170 and compares the detected current with an internallyset current value. If the detected current exceeds the specified currentvalue, a shutdown signal SDS is output and turns off the power supply125.

Meanwhile, if a physical distance between the power supply 125 and thepower controller 180 is rather long (in other words, in case atransmission path is long or a transmission method is different), thestrength of the shutdown signal SDS output from the power controller 180may be weakened. Similarly, due to a difference between the circuit ofthe power controller 180 and that of the power supply 125, logic levelof the shutdown signal SDS may be changed. To compensate for thischange, the power controller 180 may be comprised as described below.

As shown in FIGS. 4 and 5, the power controller comprises an analysisunit 181 and a shutdown signal generation unit 185. At this time, theanalysis unit 181 and the shutdown signal generation unit 185 can beformed in the same board together with the timing controller. Similarly,the analysis unit 181 may be formed in the same board together with thetiming controller while the shutdown signal generation unit 185 may beformed in the same board together with the power supply 125.

The analysis unit 181 receives a detected current value from the currentdetection unit 170 and compares the detected current value with aninternally set current value and outputs a digital pulse if the valuesare different from each other. The shutdown signal generation unit 185generates a shutdown signal SDS by using a digital pulse output from theanalysis unit 181.

As an example, the shutdown generation unit 185 comprises a resistor Rsand a transistor TFT as shown in FIG. 4. One end of the resistor Rs isconnected to a second power line wiring VCC (which can be connected tothe first power line wiring VDD, too) and the other end is connected toa first electrode (for example, a drain) of the transistor TFT. The gateelectrode of the transistor TFT is connected to a digital pulse outputport of the analysis unit 181; the first electrode is connected to theother end of the resistor Rs and a signal input port of the power supply125; and a second electrode (for example, a source) is connected to theground wiring GND.

As can be shown from FIG. 4, since the transistor TFT maintains aturn-off state when the digital pulse output from the analysis unit 181is a logic low level, a shutdown signal SDS corresponding to the levelof a second voltage provided to the second power line wiring VCC isoutput. Meanwhile, if the digital pulse output from the analysis unit181 is a logic high level, the transistor TFT maintains a turn-on stateand a shutdown signal SDS corresponding to the level of a low voltageprovided to the ground wiring GND is output.

For example, if the power supply 125 is turned off by the shutdownsignal SDS corresponding to the logic low level, the power supply 125 isturned off even if the digital pulse output from the analysis unit 181becomes the logic high level. Different from the above example, if thepower supply 125 is turned off by the shutdown signal SDS correspondingto the logic high level, the power supply is turned off even if thedigital pulse output from the analysis unit 181 becomes the logic lowlevel. At this time, it should be noted that even if level of thedigital pulse output from the analysis unit 181 changes, it iscompensated by the transistor TFT constituting the shutdown signalgeneration unit 185 and a power supply connected to the transistor TFT.

As another example, the shutdown signal generation unit 185 comprises aNAND gate (or an inverter), a resistor Rs, and a transistor TFT, asshown in FIG. 5. Two input ports of the NAND gate are connected to adigital pulse output port of the analysis unit 181 and the output of theNAND gate is connected to the gate electrode of the transistor TFT. Oneend of the resistor Rs is connected to a second power line wiring VCC(which can be connected to the first power line wiring VDD, too) and theother end is connected to a first electrode (for example, the drain) ofthe transistor TFT. The gate electrode of the transistor TFT isconnected to the output port of the NAND gate; the first electrode isconnected to the other end of the resistor Ts and a signal input port ofthe power supply 125; and the second electrode (for example, the source)is connected to the ground wiring GND.

As can be shown from FIG. 5, since the transistor TFT maintains aturn-off state when the digital pulse output from the analysis unit 181is a logic high level, a shutdown signal SDS corresponding to the levelof a second voltage provided to the second power line wiring VCC isgenerated. Meanwhile, if the digital pulse output from the analysis unit181 is a logic low level, the transistor TFT maintains a turn-on stateand a shutdown signal SDS corresponding to the level of a low voltageprovided to the ground wiring GND is generated.

For example, if the power supply 125 is turned off by the shutdownsignal SDS corresponding to the logic low level, the power supply 125 isturned off even if the digital pulse output from the analysis unit 181becomes the logic low level. Different from the above example, if thepower supply 125 is turned off by the shutdown signal SDS correspondingto the logic high level, the power supply is turned off even if thedigital pulse output from the analysis unit 181 becomes the logic highlevel. At this time, it should be noted that even if level of thedigital pulse output from the analysis unit 181 changes, it iscompensated by the transistor TFT constituting the shutdown signalgeneration unit 185 and a power supply connected to the transistor TFT.

The configurations shown in FIGS. 4 and 5 described above are valid whenthe transmission path (in other words, an interface) between theanalysis unit 181 and shutdown signal generation unit 185 employs theminiLVDS interface.

In what follows, operation states of the power controller 180 and thepower supply 125 according to control of the timing controller will bedescribed.

As shown in FIGS. 1 to 8, the timing controller 130 provides a sensingsignal SS to the power controller 180 in order for the power controller180 to operate in the blank intervals VB excluding the image displayinterval (1 frame) of the panel 160. The blank interval VB refers to avertical blank formed between vertical synchronization signals Vsyncidentifying frames. The “DE” not explained refers to a data enablesignal and “DATA” refers to a data signal output from the timingcontroller 130.

While maintaining the sensing signal SS at logic low during the imagedisplay interval (1 frame), the timing controller 130 converts thesensing signal SS to logic high H during the blank interval VB. Thepower controller 180 can determine whether the current detection unit170 detects an overcurrent in response to the sensing signal SS of logichigh H. At this time, a criterion for determining the occurrence of anovercurrent, as described earlier, employs a method of comparing adetected current with an internally set current value.

If a detected current value corresponds to “Ab(A)” which is larger thana predetermined current value “N(A)”, it indicates an abnormal statewhere an overcurrent is detected and the power controller 180 outputs ashutdown signal SDS. Since the power supply 125 is turned off inresponse to the shutdown signal SDS, an output voltage of the outputport Vout of the power supply is cut off. On the other hand, if adetected current value is similar to or the same as the predeterminedcurrent value “N(A)”, it indicates a normal state where an overcurrentis not detected and the power supply 125 outputs an output voltagethrough the output port Vout.

Meanwhile, in case the current detection unit 170 consists only ofpassive elements, the current detection unit 170 continuously detectsand outputs a current flowing through the power line wiring VDD,independently of the sensing signal SS driving the power controller 180.However, in case the current detection unit 170 comprises active andpassive elements at the same time, the current detection unit 170, inthe same manner as the power controller 180, detects and outputs acurrent flowing through the power line wiring VDD for a blank intervalexcluding the image display interval (1 frame) of the panel.

As described above, in case the timing controller 130 outputs a sensingsignal SS driving the power controller 180 only for the blank intervalVB, a current value detection time is very short compared with “T2” ascan be seen from the period of “T1”. Therefore, instead of generating aone-off sensing signal SS driving the power controller 180, the timingcontroller 130 may generate continuously N (where N is an integer two ormore) sensing signals SS1, SS2 driving the power controller 180 for eachblank interval VB.

The timing controller 130 not only periodically provides the panel 160through the data driving unit 150 with sensing data stored internallybut also provides a sensing signal SS to the power controller 180 inorder for the power controller 180 to operate in synchronization with atiming at which the sensing data is displayed. Sensing data has beendescribed with reference to black data representing a black color but isnot limited to the above, which may comprise data requiring a smallamount of data for image display. For example, sensing data can bedisplayed when a screen protector is used, a screen protector isdisplayed on the panel 160, or the whole image displayed on the panel160 is converted into another image but the present invention is notlimited to the above examples.

The timing controller 130 maintains the sensing signal SS at logic low Lduring an image display interval (1 frame) but converts the sensingsignal SS to logic high H during which the sensing data such as blackdata is displayed. The power controller 180 can detect whether a currentvalue corresponding to an overcurrent has occurred from the currentdetection unit 170 in response to the sensing signal SS of logic high H.At this time, a criterion for determining the occurrence of anovercurrent, as described earlier, employs a method of comparing adetected current with an internally set current value.

If a detected current value corresponds to “Ab(A)” which is larger thana predetermined current value “N(A)”, it indicates an abnormal statewhere an overcurrent is detected and the power controller 180 outputs ashutdown signal SDS. Since the power supply 125 is turned off inresponse to the shutdown signal SDS, an output voltage of the outputport Vout of the power supply is cut off. On the other hand, if adetected current value is similar to or the same as the predeterminedcurrent value “N(A)”, it indicates a normal state where an overcurrentis not detected and the power supply 125 outputs an output voltagethrough the output port Vout.

Meanwhile, in case the current detection unit 170 consists only ofpassive elements, the current detection unit 170 continuously detectsand outputs a current flowing through the power line wiring VDD,independently of the sensing signal SS driving the power controller 180.However, in case the current detection unit 170 comprises active andpassive elements at the same time, the current detection unit 170, inthe same manner as the power controller 180, detects and outputs acurrent flowing through the power line wiring VDD for an interval duringwhich sensing data such as black data is displayed on the panel 160.

As described above, in case the timing controller 130 outputs a sensingdata and a sensing signal SS operating the power controller 180 insynchronization with a timing at which the sensing data is displayed, ascan be noticed from the period of “T2”, an advantageous effect isobtained that a current value detection time becomes long compared with“T1”.

As shown in FIG. 9, a circuit controlling the power supply 125 comprisesa timing controller 130, a current detection unit 170, and a powercontroller 180. A power controller 180 according to a modified exampleincludes an inverter INV between the timing controller 130 and the powercontroller 180.

Although the structure of FIG. 3 assumes that the timing controller 130generates a separate sensing signal SS, the structure of FIG. 9 can beused when the timing controller 130 is equipped with a port generating avertical synchronization signal Vsync. The inverter INV inverts thevertical synchronization signal Vsync and outputs a logic high levelduring the “VB” interval of FIG. 6. Therefore, the structure of FIG. 9,by employing the inverter INV, can control the power controller 180 andthe power supply 125 as shown in FIG. 6.

Meanwhile, the method as shown in FIG. 9 controls the power controller180 and the power supply 125 during the “VB” interval. When the timingcontroller 130 does not have an output port for the verticalsynchronization signal Vsync, a data enable signal DE output from thetiming controller 130 may be utilized. To this purpose, a countercircuit may be installed between the timing controller 130 and the powercontroller 180 instead of the inverter INV; the enable signal DE iscounted by using the counter circuit; and the “VB” interval is detectedand used as the sensing signal SS.

The first embodiment described above can be applied to the structurewhere the first power line wiring VDD in the panel 160 is connected toeach other. The first embodiment can be implemented by employing anorganic light emitting display device as described below.

As shown in FIG. 10, a plurality of scan driving units 140 are formed ina non-display area NA located at the outer periphery of a display areaAA of the panel 160. The scan driving unit 140 is formed in the panel160 in the form of a gate-in panel along with a transistor process forsub-pixels. The data driving unit 150 is implemented in the form of aplurality (for example, four) of integrated circuits (ICs) and installedon a plurality (for example, four) of flexible printed circuit boards155; one end of the data driving unit 150 is attached to a pad unit ofthe panel 160 by employing the FOG method and the other end is attachedto a plurality (for example, two) of source circuit boards 157.

The timing controller 130, the current detection unit 170, and the powercontroller 180 are formed on the control circuit board 134. The sourcecircuit board 157 and the control circuit board 134 are connected toeach other by a flexible printed circuit board 137.

In case an organic light emitting display device is implemented asdescribed above, a first voltage output from the power supply 125 isprovided through all the first power line wiring CDD covering from thecontrol circuit board 134 to the panel 160.

In this case, since the first power line wiring VDD is connectedtogether with each other from the control circuit board 134 to the panel160, it suffices to connect one current detection unit 170 to anarbitrary point of the first power line wiring VDD. As describedearlier, this structure generates a shutdown signal SDS in the event ofovercurrent and turns off the power supply 125 formed in the systemboard.

In what follows, a method for operating an organic light emittingdisplay device according to the first embodiment of the presentinvention will be described with reference to FIGS. 1 to 10; however,the operation method of FIG. 11 only represents methods utilizing one ormore configurations described earlier but is not limited to thedescription.

First, the panel 160 displays an image S110. Next, a sensing signal SSis provided to the power controller 180, S120. Then a current isdetected by using the current detection unit 170 connected to the firstpower line wiring VDD, S130. Next, a detected current value is comparedwith a current value predetermined internally for the power controller180, S140. Next, it is determined whether the detected current value islarger than the predetermined current value S150; if the detectedcurrent value is smaller than the predetermined current value N, it isdetermined to be operating in a normal manner S160. On the other hand,if the detected current value exceeds the predetermined current value Y,it is determined to be operating in an abnormal manner S170. And ashutdown signal SDS for turning off the power supply 125 is output S180.The above process is repeated continuously or carried out at apredetermined time period.

<Second embodiment>

As shown in FIGS. 1 and 12, a circuit controlling the power supply 125comprises a timing controller 130, a current detection unit 170, and apower controller 180. A control block according to a second embodimentis applied to the case where the panel 160 uses first power line wiringVDD wired up for individual blocks.

The current detection unit 170 detects a current flowing through a firstpower line wiring VDD wired up for individual blocks and provides thepower controller 180 with the detected current values for the individualblocks. To this purpose, M (where M is an integer two or more) currentdetection units 170 are incorporated. For example, in case the firstpower line wiring VDD is divided into four blocks, the current detectionunit 170 comprises a first current detection unit 170 a detecting acurrent of a power line wiring 1 a VDDa to a fourth current detectionunit 170 d detecting a current of a power line wiring 1 d VDDd.

The current detection unit 170 detects a current flowing through thefirst power line wiring VDD periodically or aperiodically. If thecurrent detection unit 170 detects a current flowing through the firstpower line wiring VDD regularly and it is controlled by a particulardevice, it can be implemented by using OP amps. On the other hand, ifthe current detection unit 170 detects a current flowing aperiodicallythrough the first power line wiring VDD while being controlled by aparticular device, it can be implemented by using conventional OP ampsand switches. In this case, a switch detects a current in accordancewith a control signal.

The timing controller 130 provides a sensing signal SS to the powercontroller 180. The timing controller 130 can not only provide a panelwith sensing data through a data driving unit periodically but alsoprovide the power controller 180 with the sensing signal SS in order forthe power controller 180 to operate in synchronization with a timing atwhich the sensing data is displayed. On the other hand, the timingcontroller 130 can provide the sensing signal SS to the power controller180 in order for the power controller 180 to operate for blank intervalsexcluding an image display interval of the panel.

The power controller 180 receives detected current values of individualblocks from the current detection unit 170 and compares the detectedcurrent values of the individual blocks with each other. A shutdownsignal SDS is generated and turns off the power supply 125 if a currenthigher or lower than the currents of the other blocks is detected.

Meanwhile, if a physical distance between the power supply 125 and thepower controller 180 is rather long (in other words, in case atransmission path is long or a transmission method is different), thestrength of the shutdown signal SDS output from the power controller 180may be weakened. Similarly, due to a difference between the circuit ofthe power controller 180 and the circuit of the power supply 125, logiclevel of the shutdown signal SDS may be changed. To compensate for thischange, the power controller 180 may be implemented as shown in FIG. 4or 5.

In the second embodiment, a criterion based on which an overcurrent hasoccurred employs a method of comparing detected current values ofindividual blocks with each other.

As shown in FIG. 13, if a current value of a third block among detectedcurrent values of blocks (BL1˜BL4) corresponds to “Ab(A)” which islarger than the current values “N(A)” of the 1, 2, and 4 block (BL1,BL2, and BL4), it indicates an abnormal state where an overcurrent isdetected and the power controller 180 outputs a shutdown signal SDS.Since the power supply 125 is turned off in response to the shutdownsignal SDS, an output voltage of the output port Vout of the powersupply is cut off. On the other hand, if detected current values ofindividual blocks are similar to or the same as each other, it indicatesa normal state where an overcurrent is not detected and the power supply125 outputs an output voltage through the output port Vout.

Meanwhile, the amount of current consumption for each block of the firstpower line wiring may differ from each other according to the imagedisplayed on the panel 160. Therefore, in this situation, it may beadvantageous to set up a permissible error range. Therefore, the powercontroller 180 may be designed in such a way that if detected currentvalues of individual blocks fall within the error range, the shutdownsignal SDS is not generated whereas a detected current value of a blockgets out of the error range, the shutdown signal SDS is generated.

As shown in FIG. 14, a first power line wiring VDD is disposed in such away that wiring is distinguished for each individual block of the panel160. For example, the first power line wiring is disposed to form fourblocks of 1 a to 1 b power line wiring VDDa VDDd for each individualregion of the panel 160.

A plurality of scan driving units 140 are formed in a non-display areaNA located at the outer periphery of a display area AA of the panel 160.The scan driving unit 140 is formed in the panel 160 in the form of agate-in panel along with a transistor process for sub-pixels. The datadriving unit 150 is implemented in the form of a plurality (for example,four) of integrated circuits (ICs) and installed on a plurality (forexample, four) of flexible printed circuit boards 155; one end of thedata driving unit 150 is attached to a pad unit of the panel 160 byemploying the FOG method and the other end is attached to a plurality(for example, two) of source circuit boards 157.

The timing controller 130, the current detection unit 170, and the powercontroller 180 are formed on the control circuit board 134. The sourcecircuit board 157 and the control circuit board 134 are connected toeach other by a flexible printed circuit board 137.

In case an organic light emitting display device is implemented asdescribed above, a first voltage output from the power supply 125 isfirst provided through the first power line wiring VDD and then providedthrough four branches of power line wiring 1 a to 1 d (VDDa VDDd) afterthe source circuit board 157.

In this case, since the power line wiring branches into foursub-divisions, it suffices to connect the first to the fourth currentdetection unit 170 a-170 d for each branch point. As described earlier,this structure outputs a shutdown signal SDS in the event of overcurrentand turns off the power supply 125 formed in the system board.

In what follows, a method for operating an organic light emittingdisplay device according to the second embodiment of the presentinvention will be described with reference to FIGS. 1, 12, and 15;however, the operation method of FIG. 15 only represents methodsutilizing one or more configurations described earlier but is notlimited to the description.

First, the panel 160 displays an image S210. Next, sensing data (forexample, black data) is provided to the panel 160, S220. Next, currentsare detected by using the first to the fourth current detection unit 170a-170 d connected to the power line wiring for individual groups 1 a to1 d (VDDa˜VDDd) S230. Then, detected current values of individual blocksfrom the first to the fourth current detection unit 170 a-170 d arecompared with each other S240. Next, it is determined whether thedetected current values of individual blocks are identical to (orsimilar to) or within a permissible error range S250. If the detectedcurrent values of individual blocks are identical (or similar) to orwithin a permissible error range Y, it is determined to be operating ina normal manner S260. On the other hand, if a detected current value ishigher or lower than the other current values N, it is determined to beoperating in an abnormal manner S270. And a shutdown signal SDS forturning off the power supply 125 is output S280. The above process isrepeated continuously or carried out at a predetermined time period.

Meanwhile, the present invention assumes that a current flowing througha first power line wiring is detected to solve a short circuit problembetween power terminals. However, in the event of short circuit betweenthe first power line wiring and the ground wiring, currents are made toflow between the first power line and the ground wiring; therefore, itmay be still acceptable to have current detection units at the groundwiring rather than the first power line wiring. Also, since variousvoltages (in addition to VCC, VDD shown in FIG. 1) are employed in caseof an organic light emitting display device, power line wiring is notlimited only to the first power line wiring described above.

Moreover, the power controller described in FIGS. 3, 4, 5, 9, 10, and 14of the present invention can be incorporated into the timing controller.In this case, the current detection unit further incorporates ananalog-to-digital converter which converts a detected analog currentvalue to a digital current value. Accordingly, the power controllerincluded in the timing controller according to the first embodiment candetermine based on the digital current value obtained from theanalog-to-digital converter whether a detected current value gets out ofa range set internally. Meanwhile, the power controller included in thetiming controller according to the second embodiment can determine basedon the digital current value obtained from the analog-to-digitalconverter whether a detected current value from a particular block ishigher or lower than the current values of the other blocks.

As described above, the present invention can provide an organic lightemitting display device and a method for operating the device, capableof preventing a local burning out from being spread to the whole system(burning out the sub-pixel and its adjacent sub-pixels) as excessivecurrents flow into the elements included in sub-pixels due to theoccurrence of short circuit between power terminals and thus removing apossibility of being led to a fire. Also, the present invention canprovide an organic light emitting display device and a method foroperating the device, capable of controlling the power supply by using ashort-circuit detection circuit which can be modified into various formsand cope with various cases according to configurations of the device.

<Third embodiment>

As shown in FIG. 31, an organic light emitting display device accordingto a third embodiment of the present invention comprises an imageprocessing unit 120, a power supply 125, a timing controller 130, a datadriving unit 150, a scan driving unit 140, a panel 160, a compensationvoltage supply 170, and a voltage sensing unit 180.

An image processing unit 120 provides a timing controller 130 with avertical synchronization signal (Vsync), a horizontal synchronizationsignal (Hsync), a data enable signal (DE), a clock signal (CLK), and adata signal (DATA). The image processing unit 120 is formed in a systemboard 110.

The timing controller 130 controls an operation timing of the datadriving unit 150 and the scan driving unit 140 by using timing signalssuch as the vertical synchronization signal (Vsync), the horizontalsynchronization signal (Hsync), the data enable signal (DE), and theclock signal (CLK). Since the timing controller 130 is capable ofdetermining a frame interval by counting the data enable signal (DE)during one horizontal interval, the vertical synchronization signal(Vsync) and the horizontal synchronization signal (Hsync) provided fromthe outside can be omitted. Control signals generated at the timingcontroller 130 include a gate timing control signal (GDC) forcontrolling the operational timing of the scan driving unit 140 and adata timing control signal (DDC) for controlling the operational timingof the data driving unit 150. The gate timing control signal (GDC)includes a gate start pulse, a gate shift clock, and a gate outputenable signal. The data timing control signal (DDC) includes a sourcestart pulse, a source sampling clock, and a source output enable signal.

The scan driving unit 140 shifts the level of a gate driving voltage inresponse to the gate timing control signal (GDC) provided from thetiming controller 130 and generates a scan signal in a sequentialmanner. The scan driving unit 140 provides a scan signal through scanlines (SL1˜SLm) connected to sub-pixels (SPs) included in the panel 160.

The data driving unit 150 performs sampling of the data signal (DATA)provided from the timing controller 130 in response to the data timingcontrol signal (DDC) provided from the timing controller 130 and latcheson the sampled data signal and transforms the latched, sampled datasignal into the data of a parallel data system. The data driving unit150 transforms the data signal (DATA) into a gamma reference voltage.The data driving unit 150 provides the data signal (DATA) through thedata lines (DL1˜DLn) connected to sub-pixels (SPs) included in the panel160.

The power supply 125 converts an external voltage supplied from theoutside into a first voltage (for example, 20 V level), a second voltage(for example, 3.3V level), and a low voltage (for example, 0 V level),and so on. The first voltage, being supplied to a first power linewiring EVDD, is a drain level voltage; the second voltage, beingsupplied to a second power line wiring VCC, is a collector levelvoltage; and the low level voltage is supplied to the ground EVSS, GNDand is a base level voltage. The power supply 125 is formed in thesystem board 110 together with the image processing unit 120. The outputvoltage of the power supply 125 is used for the image processing unit120, the timing controller 130, the data driving unit 150, the scandriving unit 140, the panel 160, and the compensation voltage supply170.

The compensation voltage supply 170 outputs a compensation voltageVinit, Vref. The compensation voltage Vinit, Vref includes aninitialization voltage Vinit and a reference voltage Vref. Theinitialization voltage Vinit and the reference voltage Vref may beidentical to each other or may have different levels from each other.The initialization voltage Vinit and the reference voltage Vref outputfrom the compensation voltage supply 170 are provided to compensationcircuits included in sub-pixels (SPs) of the panel 160. As shown in FIG.32(a), the compensation voltage supply 170 can output the initializationvoltage Vinit and the reference voltage Vref by using a voltage outputfrom the power supply 125. As shown in FIG. 32(b), the compensationvoltage supply 170 can be divided into a first compensation voltagesupply 170 a generating the initialization voltage Vinit and a secondcompensation voltage supply 170 b generating the reference voltage Vrefby using a voltage output from the power supply 125. Different from theabove, as shown in FIG. 33, the compensation voltage supply 170 cangenerate the initialization voltage Vinit and the reference voltage Vrefby using a voltage output from the inside of the data driving unit 150.

The voltage sensing unit 180 senses a compensation voltage Vinit, Vrefoutput from the compensation voltage supply 170 and outputs the sensedvoltage. The voltage sensing unit 180 separately senses theinitialization voltage Vinit and the reference voltage Vref output fromthe compensation voltage supply 170. The compensation voltage Vinit,Vref sensed by the voltage sensing unit 180 is used as a criterion basedon which the timing controller 130 generates a shutdown signal SDS forturning off the power supply 125.

The panel 160 comprises sub-pixels disposed in the form of a matrix.Sub-pixels consist of red, green, and blue sub-pixels; in some cases,white sub-pixels are included. A panel 160 incorporating whitesub-pixels can emit white light even if light emitting layers ofindividual sub-pixels do not emit red, green, and blue light. In thiscase, the white light is converted into red, green, and blue light by anRGB color filter.

Meanwhile, sub-pixels included in the panel 160 may be comprised asfollows.

As shown in FIG. 34, one sub-pixel comprises a switching transistor SW,a driving transistor DR, a capacitor Cst, a compensation circuit CC, andan organic light emitting diode D. In case a compensation circuit CC isincluded, one scan line SL1 comprises a first scan line EM, a secondscan line INIT, and a third scan line SCAN.

The compensation circuit CC compensates for a threshold voltage of adriving transistor and the like by using the initialization voltageVinit and the reference voltage Vref. A sub-pixel incorporating thecompensation circuit CC detects a threshold voltage of the drivingtransistor DT by using a diode connection method, a source-followingmethod, and so on. Since there are a large volume of reference documentsfor the diode connection method, further description thereof will not begiven in this document; instead, the source-following method will bedescribed as follows.

The source-following method inserts a compensation capacitor between thegate-source electrode of the driving transistor DT and in the event ofdetecting a threshold voltage, makes the source voltage of the drivingtransistor DT follow the gate voltage. Moreover, since the drain voltageof the driving transistor DT is separated from the gate electrode andreceives a power voltage from a first power line wiring EVDD, thesource-following method is enabled to detect a negative-valued thresholdvoltage as well as a positive-valued threshold voltage.

Moreover, the source-following method makes the gate electrode of thedriving transistor float in the event of sensing a threshold voltage ofthe driving transistor DT and improves compensation capability of athreshold voltage by using a compensation capacitor installed betweenthe gate-source electrode of the driving transistor DT and a parasiticcapacitor of the driving transistor DT.

The compensation circuit CC comprises one or more transistors andcapacitors; in the following, circuit configuration of a sub-pixel inFIG. 34 will be described more specifically by using one example ofcompensation circuit for which the source-following method has beenapplied described above.

As shown in FIG. 35, the compensation circuit CC comprises a firsttransistor ST1, a second transistor ST2, a third transistor ST3, and acompensation capacitor Cgs. In what follows, the compensation circuit CCis introduced for the convenience of description only; the thirdembodiment of the present invention is not limited to the descriptionsbelow but can be used for all the structure for compensating for athreshold voltage of the driving transistor DT by using the referencevoltage Vref.

A first transistor ST1 provides a data voltage stored in a node A to anode B in response to a light emission control signal (em) providedthrough a first scan line EM. The gate electrode of the first transistorST1 is connected to the first scan line EM; a first electrode isconnected to the node A while a second electrode is connected to thenode B. The first transistor ST1 is a node voltage switching transistor.

A second transistor ST2 provides an initialization voltage Vinit to anode C in response to an initialization signal (init) provided through asecond scan line INIT. The gate electrode of the second transistor ST2is connected to the second scan line INIT; a first electrode isconnected to the node C while a second electrode is connected to aninitialization voltage terminal VINIT. The second transistor ST2 is aninitialization voltage supply transistor.

A third transistor ST3 provides a reference voltage Vref to a node B inresponse to an initialization signal (init) provided through a secondscan line INIT. The gate electrode of the third transistor ST3 isconnected to the second scan line INIT; a first electrode is connectedto the node B while a second electrode is connected to a referencevoltage terminal VREF. The third transistor ST3 is a reference voltagesupply transistor.

The compensation capacitor Cgs renders the source-following methodapplicable in the event of detecting a threshold voltage of the drivingtransistor DT and contributes to improving the capability ofcompensating for the threshold voltage. The gate electrode of thedriving transistor DT is connected to one end of the compensationcapacity Cgs and the node C is connected to the other end thereof.

As the compensation circuit CC is configured as described above, theswitching transistor SW provides a data voltage Vdata to the node A inresponse to a switching signal (scan) provided through the third scanline SCAN. The gate electrode of the switching transistor SW isconnected to the third scan line SCAN; the first electrode is connectedto the node A while the second voltage is connected to a first data lineDLL One end of a storage capacitor Cst is connected to the node A whilethe other end of the storage capacitor Cst is connected to the node C.The gate electrode of the driving transistor DT is connected to the nodeB; the first electode is connected to the node C while the secondvoltage is connected to a first power line wiring EVDD. The anode of anorganic light emitting diode (OLED) is connected to the node C while thecathode of the OLED is connected to the ground wiring EVSS. In thedescription above, it was assumed that the source electrode oftransistors is selected as the first electrode, while the drainelectrode thereof as the second electrode; however, the presentinvention is not limited to the assumption above.

As shown in FIG. 21, an image display interval of a sub-pixelincorporating a compensation circuit CC is divided into aninitialization interval Ti during which the node A, B, and C areinitialized into a particular voltage, a sensing interval Ts duringwhich a threshold voltage of the driving transistor DT is detected andstored, a programming interval Tp during which a data voltage Vdata isapplied, and a light emission interval Te during which a driving currentapplied to an organic light emitting diode (OLED) is compensatedindependently of a threshold voltage by using the threshold voltage andthe data voltage Vdata. Here, the light emission interval Te is furtherdivided into a first Te1 and a second light emission interval Te2. Moredetailed description related to the compensation circuit CC refers toKorean patent application no. 10-2012-0095604.

Sub-pixels incorporating a compensation circuit CC as described aboveemploys a compensation voltage Vinit, Vref for compensating for athreshold voltage of the driving transistor DT as well as a conventionaltype of power source such as a first power line wiring EVDD and groundwiring EVSS.

Since organic light emitting display panels require a large amount ofcurrents compared with the liquid crystal display panels, in case ofshort circuit at power terminals, an excessive amount of currents flowsinto the elements of the respective sub-pixels. Various factors causeshort circuit at power terminals, which include not only internal,structural factors such as particles introduced into the organic lightemitting display panel during manufacturing process (or module process),cracks, misalignment of pad units, and narrow wiring layout; but alsoexternal factors such as static electricity.

If short circuit occurs at power terminals, a change occurs subsequentlyin the compensation voltage Vinit, Vref. According to a third embodimentof the present invention, the compensation voltage Vinit, Vrefinfluenced by short circuit at power sources is sensed and occurrence ofshort circuit is checked and accordingly, power source of the powersupply is cut off, which will be described in more detail below.

As shown in FIG. 22, the compensation voltage supply 170 generates acompensation voltage Vinit, Vref including the initialization voltageVinit and the reference voltage Vref. The compensation voltage supply170 is realized by one of the examples shown in FIGS. 32 and 33.

The voltage sensing unit 180 comprises a first voltage sensing unit 181sensing the initialization voltage Vinit and a second voltage sensingunit 182 sensing the reference voltage Vref. The first and the secondvoltage sensing unit 181, 182 compares the sensed compensated voltageVinit, Vref with an internally set threshold voltage and outputs thecomparison result.

The timing controller 130 includes a short-circuit detection unit 135.The short-circuit detection unit 135 generates a shutdown signal SDS forturning off the power supply 125 based on the results obtained from thefirst 181 and the second voltage sensing unit 182.

The first 181 and the second voltage sensing unit 182 differ in thevoltages provided to a first and a second threshold voltage terminal buthave structures which are the same as or similar to each other.Therefore, in what follows, descriptions of the present invention willbe given with reference to the second voltage sensing unit 182 as arepresentative example.

As shown in FIG. 23, the compensation voltage supply 170 amplifies anexternal voltage source Vin and outputs a reference voltage Vref. It isassumed that the compensation voltage supply 170 comprises an amplifierOPV and resistors R1, R2, R3. A first resistor R1 has it one endconnected to the external voltage source Vin and the other end of thefirst resistor R1 is connected to a first terminal (−) of the amplifierOPV. One end of a second resistor R2 is connected to a second terminal(+) of the amplifier while the other end of the second resistor R2 isconnected to a third terminal (O) of the amplifier OPV. One end of athird resistor R3 is connected to a third terminal of the amplifier OPVwhile the other end of the third resistor R3 is connected to an outputterminal of the amplifier OPV.

The second voltage sensing unit 182 senses the reference voltage Vref.The second voltage sensing unit 182 comprises a first comparator Comp1sensing the minimum level of the reference voltage Vref and a secondcomparator Comp2 sensing the maximum level of the reference voltageVref. A first terminal (−) of the first comparator is connected to afirst threshold voltage terminal (−V1) and a second terminal (+) of thefirst comparator is connected to an output terminal of the compensationvoltage supply 170 and an output terminal (O) of the first comparator isconnected to the short-circuit detection unit 135. A first terminal (−)of the second comparator is connected to an output terminal of thecompensation voltage supply 170 and a second terminal (+) of the secondcomparator is connected to the second threshold voltage terminal (−V2)and an output terminal of the second comparator is connected to theshort-circuit detection unit. A negative voltage is employed for thevoltage provided to the first (−V1) and the second threshold voltageterminal (−V2).

The first Comp1 and the second comparator Comp2 compare a sensedreference voltage with the first and the second threshold voltageinternally set; and determine whether the minimum and the maximum levelof the reference voltage gets out of a permissible range specified; andoutput the result.

As shown in FIG. 10, a plurality of scan driving units 140 are formed ina non-display area NA located at the outer periphery of a display areaAA of the panel 160. The scan driving unit 140 is formed in the panel160 in the form of a gate-in panel along with a transistor process forsub-pixels. The data driving unit 150 is implemented in the form of aplurality (for example, four) of integrated circuits (ICs) and installedon a plurality (for example, four) of first flexible printed circuitboards 155; one end of the data driving unit 150 is attached to a padunit of the panel 160 by employing the FOG method and the other end isattached to a plurality (for example, two) of source circuit boards 157.

The timing controller 130, the compensation voltage supply 170, and thevoltage sensing unit 180 are formed on the control circuit board 134.The source circuit board 157 and the control circuit board 134 areconnected to each other by a second flexible printed circuit board 137.The image processing unit 120 and the power supply 125 are formed on thesystem board 110. The control circuit board 134 and the system board 110are connected to each other by a third flexible printed circuit board115.

In case an organic light emitting display device is implemented asdescribed above, a compensation voltage generated at the compensationvoltage supply 170 is provided through the wiring which passes throughthe control circuit board 134 and reaches up to the panel 160.

Meanwhile, the description above assumed that the compensation voltagesupply 170 and the voltage sensing unit 180 are formed on the controlcircuit board 134. However, it should be noted that the voltage sensingunit 180 may be formed at various positions including the source circuitboard 157.

In the following, output of a shutdown signal and output states of thepower supply will be described with one example illustrating a casewhere a reference voltage gets out of a permissible range along withindication of a minimum and a maximum level of the reference voltage.

As shown in FIG. 25, the reference voltage Vref is output being fixed ata particular voltage or output being varied within a particular voltagerange. In what follows, it is assumed that the reference voltage Vref isoutput being fixed at a voltage level of −2.2V while a permissible rangeof the minimum level is set at a voltage level of −1V and a permissiblerange of the maximum level is set at a voltage level of −4V.

In this case, the permissible range for the reference voltage Vref asshown in FIG. 26 becomes 43V level. Thus the first threshold voltage ofFIG. 23 provided to the first threshold voltage terminal (−V1) becomes−1V while the second threshold voltage of FIG. 23 provided to the secondthreshold voltage terminal (−V2) becomes −4V.

<The Case where the Minimum and the Maximum Level of a Reference VoltageRanges Between −1V and −4V>

The minimum level of reference voltage sensed by a first comparatorComp1 and the maximum level of reference voltage sensed by a secondcomparator Comp2 ranges between −1V and −4V. In this case, theshort-circuit detection unit 135 regards the power source of the panelas normal as shown in FIG. 26 and generates a shutdown signal SDS oflogic low (L) as shown for a first interval Ti of FIG. 27 (or it maygenerate no signal). At this time, the power supply 125 maintains outputof the output terminal Vout.

<The Case where the Minimum and the Maximum Level of a Reference VoltageGets Out of a Range Between −1V and −4V>

The minimum level of reference voltage sensed by a first comparatorComp1 and the maximum level of reference voltage sensed by a secondcomparator Comp2 get out of a range between −1V and −4V. In this case,the short-circuit detection unit 135 regards the power source of thepanel as abnormal as shown in FIG. 26 and generates a shutdown signalSDS of logic high (H) as shown for a second interval T2 of FIG. 27. Atthis time, the power supply 125 stops providing an output through theoutput terminal Vout and is turned off.

Meanwhile, the example above assumed that the power supply 125 is turnedoff only if a shutdown signal SDS of logic high (H) is generated.However, the power supply 125 can be so designed to be turned off if ashutdown signal SDS of logic low (L) is generated.

In what follows, a method for operating an organic light emittingdisplay device according to the third embodiment of the presentinvention will be described with reference to FIGS. 1 to 28; however,the operation method of FIG. 28 only represents methods utilizing one ormore configurations described earlier but is not limited to thedescription.

First, the panel 160 displays an image S110. Next, a compensationvoltage Vinit, Vref provided to the panel 160 is sensed S120. Then thecompensation voltage Vinit, Vref is compared with a threshold voltage−V1, −V2, S130. Next, if the reference voltage Vinit, Vref falls withina permissible range without getting out of the threshold voltage −V1,−V2 (N), it is regarded as normal S150; and does not generate a shutdownsignal SDS for turning off the power supply 125 which provides power tothe panel 160. Afterwards, the panel 160 continues to display images.

Different from the above, if the compensation voltage Vinit, Vrefexceeds the threshold voltage −V1, −V2, escaping the permissible rangefor the reference voltage, it is regarded as abnormal S160 and generatesa shutdown signal SDS for turning off the power supply 125 whichprovides power to the panel 160, S170. Afterwards, the panel 160 doesnot display images.

As described above, the third embodiment of the present inventionprovides an organic light emitting display device and a method foroperating the device, capable of controlling the power supply in theevent of short circuit at the power source or in the case of anovercurrent by sensing a compensation voltage provided when sub-pixelsincorporate a compensation circuit.

<Fourth embodiment>

As shown in FIG. 29, an organic light emitting display device accordingto a fourth embodiment of the present invention comprises an imageprocessing unit 120, a power supply 125, a timing controller 130, a datadriving unit 150, a scan driving unit 140, a panel 160, a currentsensing unit 190, and an analog-to-digital converter 200.

In case of the fourth embodiment, sub-pixels (SPs) included in the panel160 may assume a structure incorporating a compensation circuit asdescribed in the third embodiment or a conventional structure notincorporating the compensation circuit. However, for the currentembodiment, a first power line wiring EVDD in the panel 160 is wired upseparately for individual blocks. Since the image processing unit 120,the power supply 125, the data driving unit 150, and the scan drivingunit 140 are configured to operate in the same way as the thirdembodiment, further description thereof will not be provided.

The current sensing unit 190 senses a current flowing through the firstpower line wiring EVDD wired up for individual blocks and amplifies thesensed currents of the individual blocks into the corresponding analogvoltages and outputs the analog voltages.

The analog-to-digital converter 200 converts an analog voltage of eachblock provided from the current sensing unit 190 into the correspondingdigital voltage and outputs the digital voltage.

The timing controller 130 receives a digital voltage of each blockthrough communication with the analog-to-digital converter 200 anddetermines occurrence of a short-circuit or an overcurrent in the panel160 by using the digital voltage of each block and in the event of ashort-circuit or an overcurrent, generates an shutdown signal SDS forturning off the power supply 125. In what follows, it is assumed that acommunication interface between the timing controller 130 and theanalog-to-digital converter 200 employs SPI (Serial PeripheralInterface), which is a serial communication method.

Different from the third embodiment, the first power line wiring EVDDformed in the panel 160 of the fourth embodiment is wired up separatelyfor individual blocks. And the timing controller 130 determines theoccurrence of an overcurrent in the panel 160 through the currentsensing unit 190 and the analog-to-digital converter 200 and in theevent of an overcurrent, turns off the power supply 125.

As shown in FIG. 30, the data driving unit 150 is implemented in theform of a plurality (for example, three) of integrated circuits (ICs)and installed on a plurality (for example, three) of first flexibleprinted circuit boards 155; the data driving unit 150 is attached to apad unit of the panel 160 by employing the FOG method. Although notshown in the figure, the other end of the first flexible printed circuitboard 155 is attached to a source circuit board.

The first power line wiring EVDD is split into a plurality of wiring(for example, three wirings) before it passes through the first flexibleprinted circuit board 155. Accordingly, the first power line wiring EVDDformed on the panel 160 is wired up separately for individual blocks. Inwhat follows, it is assumed that the first power line wiring EVDD formedon the panel 160 is divided into a first to a third block power linewiring EVDD1˜EVDD3.

The current sensing unit 190 comprises a first block current sensingunit 190 a to a third block current sensing unit 190 c. The first blockcurrent sensing unit 190 a senses a first block current (i1) flowingthrough the first block power line wiring EVDD1 and amplifies the sensedcurrent into a first block analog voltage SV1 and outputs the firstblock analog voltage SV1. The second block current sensing unit 190 bsenses a second block current (i2) flowing through the second blockpower line wiring EVDD2 and amplifies the sensed current into a secondblock analog voltage SV2 and outputs the second block analog voltageSV2. The third block current sensing unit 190 c senses a third blockcurrent (i3) flowing through the third block power line wiring EVDD3 andamplifies the sensed current into a third block analog voltage SV3 andoutputs the third block analog voltage SV3.

The first to the third block analog voltage SV1˜SV3 sensed by the firstblock current sensing unit 190 a to the third block current sensing unit190 c are provided to the analog-to-digital converter 200. Theanalog-to-digital converter 200 converts the first to the third blockanalog voltage SV1˜SV3 into a first to a third block digital voltage.Here, the first to the third block digital voltage are provided to thetiming controller 130 through a communication line (SPI) connecting theanalog-to-digital converter 200 and the timing controller 130.

The first 190 a to the third block current sensing unit 190 c differonly in their sensing positions but have the same structure with eachother. Therefore, in what follows, descriptions of the present inventionwill be provided by using the first block current sensing unit 190 a asa representative of the three block current sensing units.

As shown in FIG. 31, the first block current sensing unit 190 acomprises an amplifier OPR and resistors R1˜R6. The first block currentsensing unit 190 a, being installed between the first power line wiringEVDD and the first block power line wiring EVDD1, senses a first blockcurrent (i1) flowing through the first block power line wiring EVDD1 andconverts the sensed first block current (i1) into a first block analogvoltage SV1 and outputs the first block analog voltage SV1.

When converting a current into the corresponding voltage, the firstblock current sensing unit 190 a makes use of the voltages provided to apositive voltage terminal V+ and a negative voltage terminal V−. At thistime, although a scan high voltage generated by the scan driving unitmay be used as the voltage applied to the positive voltage terminal V+,the present invention is not limited to the above example.

Meanwhile, the embodiment in the figure assumed that the first blockcurrent sensing unit 190 a consists only of an amplifier OPR andresistors R1˜R6, capacitors or other passive elements may be furtherincorporated into the first block current sensing unit 190 a.

One ends of the first and the second resistor R1, R2 are connected tothe first power line wiring EVDD and the other ends are connected to thefirst block power line wiring EVDDL The third resistor R3 is connectedbetween one ends of the first and the second resistor R1, R2 and a thirdterminal 3 of the amplifier OPR. The fourth resistor R4 is connectedbetween one ends of the first and the second resistor R1, R2 and a firstterminal 1 of the amplifier OPR. The fifth resistor R5 is connectedbetween a second 2 and a third terminal 3 of the amplifier OPR and theground wiring. The sixth resistor R6 is connected between the first 1and a fourth terminal 4 of the amplifier OPR and the ground wiring. Thesecond terminal 2 is connected to the negative voltage terminal V− ofthe amplifier OPR and the fifth terminal 5 is connected to the positivevoltage terminal V+ of the amplifier OPR and a first block analogvoltage SV1 is generated through the first terminal 1.

In the following, a process of outputting a shutdown signal will bedescribed in conjunction with the analog-to-digital converter, thetiming controller, and the power supply.

As shown in FIGS. 32 to 35, the analog-to-digital converter 200 and thetiming controller 130 communicates commands through bus lines SDI, SCLK,SDO, CS included in the communication interface SPI. At this time, thetiming controller 130 is selected as a master unit and theanalog-to-digital converter is selected as a slave unit.

The timing controller 130 receives a first to an n-th block digitalvoltage SV1˜SVn from the analog-to-digital converter 200 during a blankinterval VB. The timing controller 130 receives digital voltages ofindividual blocks during at least two times of blank intervals and basedon a difference value between the digital voltages, determinesoccurrence of a short-circuit or an overcurrent. To this purpose, thetiming controller 130 comprises a determination unit 131 receivingdigital voltages of individual blocks during at least two times of blankintervals VB and determines the difference between the digital voltages;and a shutdown signal generation unit 136 generating a shutdown signalSDS according to a result of the determination unit 131.

To be more specific, the determination unit 131 receives first digitalvoltages of individual blocks about the first to the n-th block digitalvoltage SV1˜SVn from the analog-to-digital converter 200 during a firstblank interval VB of “T1”. Next, the determination unit 131 receivessecond digital voltages of individual blocks about the first to the n-thblock digital voltage SV1˜SVn from the analog-to-digital converter 200during a second blank interval VB of “T2”.

The determination unit 131 compares the first block digital voltage withthe second block digital voltage and if a difference between the twovoltages is zero, it is determined to be operating in normal conditionsrevealing no short-circuit or overcurrent. At this time, thedetermination unit 131 provides the shutdown signal generation unit 136with either a signal of logic low or no signal at all. Therefore, theoutput terminal Vout of the power supply maintains its output.

On the other hand, if a difference between the first and the secondblock digital voltage shows non-zero value and exceeds a permissiblerange, the determination unit 131 determines that an abnormal state hasoccurred, revealing a short-circuit or an overcurrent in the panel. Atthis time, the determination unit 131 provides the shutdown signalgeneration unit 136 with a signal of logic high. Subsequently, the powersupply stops its output terminal Vout and is turned off.

As a specific example, FIG. 35 illustrates a case where the first blockdigital voltage SV1 sensed during the second blank interval VB is largerthan the first block digital voltage SV1 sensed during the first blankinterval VB, exceeding a permissible range by a voltage value “Ab(V)”.

Since the first block digital voltage SV1 sensed during the second blankinterval VB exceeds the permissible range by the amount of voltage“Ab(V)”, the shutdown signal generation unit 136 generates a shutdownsignal SDS of logic high (H) instead of logic low (L). Subsequently, thepower supply 125 stops the output terminal Vout and is turned off.

Meanwhile, the determination unit 131 and the shutdown signal generationunit 136 have been functionally separated in the above description forthe convenience of understanding; therefore, the two units can becombined into a single unit in a different implementation. In addition,although the present invention assumes that the determination unit 131and the shutdown signal generation unit 136 are incorporated into thetiming controller 130, the two units can be implemented separately fromthe timing controller 130. Moreover, the permissible range introducedabove can be configured differently according to the conditions of thepanel, output voltage, and so on.

Meanwhile, constituting elements according to the fourth embodiment canbe used to implement an organic light emitting display device as in thethird embodiment of FIG. 24. At this time, the current sensing unit 190and the analog-to-digital converter 200 can be formed all in the controlcircuit board 134 or formed separately in the source circuit board 157and the control circuit board 134.

In what follows, a method for operating an organic light emittingdisplay device according to the fourth embodiment of the presentinvention will be described with reference to FIGS. 29 to 36; however,the operation method of FIG. 36 only represents methods utilizing one ormore configurations described earlier but is not limited to thedescription.

First, the panel 160 displays an image S210. Next, a first block digitalvoltage is sensed through a first to a third block power line wiringEVDD1˜EVDD3 wired up for individual blocks in the panel 160, S220. Next,a second block digital voltage is sensed through the first to the thirdblock power line wiring EVDD1˜EVDD3 wired up for individual blocks inthe panel 160, S230. Then, the first block digital voltage is comparedwith the second block digital voltage S240. Next, it is determinedwhether a difference between the first and the second block digitalvoltage exceeds a permissible range S250. Next, if the differencebetween the first and the second block digital voltage falls within thepermissible range Y, it is determined to be operating in a normal mannerS260 and a shutdown signal SDS for turning off the power supply 125which provides power to the panel 160 is not generated. Afterwards, thepanel 160 continues to display images.

Different from the above, if a difference between the first and thesecond block digital voltage exceeds a permissible range N, it isdetermined to be operating in an abnormal manner S270 and a shutdownsignal SDS for turning off the power supply 125 which provides power tothe panel 160 is generated S280. Afterwards, the panel 160 stopsdisplaying images.

As described above, the fourth embodiment of the present inventionprovides an organic light emitting display device and a method foroperating the device, capable of sensing a current flowing through afirst power line wiring wired up for individual blocks on the panel atleast two times and comparing the sensed values with each other andcontrolling the power supply in the event of a short-circuit or anovercurrent at power terminals.

As described above, the present invention can provide an organic lightemitting display device and a method for operating the device, capableof removing a possibility for a local burning out of an element to bespread to the whole system and to lead to a fire by using a circuitdetecting short circuit or an overcurrent at power terminals.

What is claimed is:
 1. An organic light emitting display device,comprising: a panel; a driving unit driving the panel; a timingcontroller controlling the driving unit; a power supply supplying powerto the panel; a current detection unit detecting a current flowingthrough power line wiring of the panel and outputting a detected currentvalue; and a power controller comparing the detected current value withan internally set current value and outputting a shutdown signal whichturns off the power supply if the detected current value exceeds thepredetermined current value, wherein the timing controller periodicallyprovides the panel with internally stored sensing data through thedriving unit and provides the power controller with a sensing signal inorder for the power controller to operate in synchronization with atiming at which the sensing data are displayed.
 2. The organic lightemitting display device of claim 1, wherein the timing controllerprovides the sensing signal to the power controller in order for thepower controller to operate in blank intervals excluding an imagedisplay interval of the panel.
 3. The organic light emitting displaydevice of claim 1, wherein the current detection unit detects thecurrent flowing through the power line wiring during which the sensingdata are displayed on the panel.
 4. The organic light emitting displaydevice of claim 1, wherein the current detection unit detects thecurrent flowing through the power line wiring for blank intervalsexcluding an image display interval of the panel.
 5. The organic lightemitting display device of claim 1, wherein the power controllercomprises: an analysis unit comparing the detected current value withthe internally set current value and outputting a digital pulse if thevalues are different from each other, and a shutdown signal generationunit generating the shutdown signal by using the digital pulse outputfrom the analysis unit.
 6. The organic light emitting display device ofclaim 1, wherein the sensing data corresponds to black data representinga black color.
 7. A method of driving an organic light emitting displaydevice, the method comprising: displaying an image on a panel;periodically providing the panel with internally stored sensing data andproviding a sensing signal; detecting a current flowing through powerline wiring of the panel in synchronization with a timing at which thesensing data are displayed based on the provided sensing signal;comparing the detected current with a current value configuredinternally; and outputting a shutdown signal which turns off a powersupply if the detected current value exceeds an internally set currentvalue.
 8. The method of claim 7, wherein the sensing signal is providedin black intervals excluding an image display interval of the panel. 9.The method of claim 7, wherein the current is detected for blankintervals excluding an image display interval of the panel.
 10. Themethod of claim 7, wherein the outputting step comprises: outputting adigital pulse if the detected current value and the internally setcurrent value are different from each other; and generating the shutdownsignal by using the output digital pulse.
 11. The method of claim 7,wherein the sensing data corresponds to black data representing a blackcolor.